Hi Monks

This is regarding regex backreference. I am not able to retrieve the matched string by writing the code below.As usual i need some enlightenment here.

#!/usr/bin/perl -w
use strict;
$_='1:A silly sentence (495,a) *BUT* one which will be useful.(3)';
print"Enter a regular expression:";
my $expression=<STDIN>;
chomp($expression);
if(/$expression/)
{
       print"The expression matches the pattern\n";
       print"\$1 is $1\n",if defined $1;
       print"\$2 is $2\n",if defined $2;
       print"\$3 is $3\n",if defined $3;
}
else
{
   print"The pattern is not found \n";
}

[download]

Output

Enter a regular expression:\w\w\w The expression matches the pattern root@# This is not printing what is stored in $1,$2 etc.. if exists.

In reply to Regex backreference by vyeddula

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.